I think this is true, in general, for protests that are based in promoting prejudice. Counter-protesting bigots shows them that their hateful, closed-minded views are unpopular and unacceptable.

Locally, there was a big pushback against teaching inclusivity in schools (2SLGBTQ+ families being represented at all, basically), and a protest was organized. And across the street from them were literally 10× as many people counter protesting to support 2SLGBTQ+ rights. There hasn't been a single anti-tans bigots protest locally since.

"No tolerance for intolerance" is a powerful counter-protest message.